Imaging device, electronic apparatus, and method of manufacturing imaging device

ABSTRACT

An imaging device includes: a photodiode configured to perform photoelectric conversion and to generate electric charge in accordance with an amount of received light; a floating diffusion section configured to accumulate the electric charge generated in the photodiode; a reading circuit configured to output a pixel signal having a voltage in accordance with a level of the electric charge accumulated in the floating diffusion section, the reading circuit including one or a plurality of transistors each having a gate that is electrically connected to a wiring used for selecting a pixel; and an insulating section extending into part or whole of a bottom surface of the floating diffusion section, part or whole of bottom surfaces of source-drain regions in the one or the plurality of transistors, or both. The photodiode, the floating diffusion section, the reading circuit, and the insulating section are provided in a semiconductor layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application in a divisional of U.S. patent application Ser. No.14/338,851, filed Jul. 23, 2014, which claims the benefit of JapanesePriority Patent Application JP 2013-157986 filed Jul. 30, 2013, theentire contents of each which are incorporated herein by reference.

BACKGROUND

The present technology relates to an imaging device, to an electronicapparatus that includes the imaging device, and to a method ofmanufacturing an imaging device.

An imaging device such as a CMOS (Complementary Metal OxideSemiconductor) image sensor or a CCD (Charge Coupled Device) has beenwidely used for, for example, a digital still camera, a digital videocamcorder, and the like. Such an imaging device may include, forexample, a photodiode, and a signal reading circuit that reads aphotoelectric conversion signal obtained by the photodiode to outside,for each pixel. The signal reading circuit may include, for example, atransfer transistor, an amplifier transistor, a reset transistor, aselection transistor, and the like (for example, see Japanese UnexaminedPatent Application Publication No. 2008-91788 (JP2008-91788A)). Thesetransistors may be shared by a plurality of photodiodes in some cases.

In order to achieve low illuminance characteristics equivalent to thoseof an existing image sensor having ultra-high sensitivity, it is desiredto reduce capacity in the signal reading circuit and to improveconversion efficiency of the imaging device. In existing technologies,for example, p-type impurity concentration of a well layer in contactwith a FD (Floating Diffusion) section or n-type impurity concentrationof the FD section is decreased to suppress p-n junction capacity (forexample, see JP2008-91788A and Japanese Unexamined Patent ApplicationPublication No. 2008-218756 (JP2008-218756A)). Moreover, for example,insulating films are provided on both sides of the FD section tosuppress the p-n junction capacity (for example, see Japanese UnexaminedPatent Application Publication No. 2012-119492 (JP2012-119492A)).

SUMMARY

In the methods disclosed in JP2008-91788A and JP2008-218756A, theimpurity concentration is decreased to increase a depletion region, andthe p-n junction capacity is suppressed thereby. Therefore, a degree offreedom in layout is limited in accordance with the increase of thedepletion region. The method disclosed in JP2008-91788A may lead todecrease in device separation performance between pixels. The methoddisclosed in JP2012-119492A suppresses the p-n junction capacity only onthe both sides of the FD section. In the methods disclosed inJP2008-91788A, JP2008-218756A, and JP2012-119492A, there may still beroom for suppressing the p-n junction capacity at a bottom surface ofthe FD section.

In the signal reading circuit, the p-n junction capacity exists also insource-drain regions of one or a plurality of transistors that each havea gate electrically connected to a wiring used for selecting a pixel.When the p-n junction capacity in the source-drain region is large,wiring delay is caused. Therefore, it is desirable to suppress the p-njunction capacity in the source-drain region. A method similar to thosedescribed above may be adopted in order to suppress the p-n junctioncapacity in the source-drain region. However, there may still be roomfor suppressing the p-n junction capacity at the bottom surface of thesource-drain regions also in this case when any of the above-describedmethods is adopted.

It is desirable to provide an imaging device capable of effectivelysuppressing the p-n junction capacity at one or both of the bottomsurface of the FD section and the bottom surface of the source-drainregion. It is also desirable to provide an electronic apparatus thatincludes the imaging device, and a method of manufacturing the imagingdevice.

According to an embodiment of the present technology, there is providedan imaging device including: a photodiode configured to performphotoelectric conversion and to generate electric charge in accordancewith an amount of received light; a floating diffusion sectionconfigured to accumulate the electric charge generated in thephotodiode; a reading circuit configured to output a pixel signal havinga voltage in accordance with a level of the electric charge accumulatedin the floating diffusion section, the reading circuit including one ora plurality of transistors each having a gate that is electricallyconnected to a wiring used for selecting a pixel; and an insulatingsection extending into part or whole of a bottom surface of the floatingdiffusion section, part or whole of bottom surfaces of source-drainregions in the one or the plurality of transistors, or both. Thephotodiode, the floating diffusion section, the reading circuit, and theinsulating section are provided in a semiconductor layer.

According to an embodiment of the present technology, there is providedan electronic apparatus including: an imaging device; and a signalprocessing circuit configured to perform a predetermined process on apixel signal outputted from the imaging device. The imaging deviceincludes: a photodiode configured to perform photoelectric conversionand to generate electric charge in accordance with an amount of receivedlight; a floating diffusion section configured to accumulate theelectric charge generated in the photodiode; a reading circuitconfigured to output a pixel signal having a voltage in accordance witha level of the electric charge accumulated in the floating diffusionsection, the reading circuit including one or a plurality of transistorseach having a gate that is electrically connected to a wiring used forselecting a pixel; and an insulating section extending into part orwhole of a bottom surface of the floating diffusion section, part orwhole of bottom surfaces of source-drain regions in the one or theplurality of transistors, or both. The photodiode, the floatingdiffusion section, the reading circuit, and the insulating section areprovided in a semiconductor layer.

In the imaging device and the electronic apparatus according to theabove-described embodiments of the present technology, the insulatingsection extends into part or whole of the bottom surface of the FDsection, part or whole of the bottom surfaces of the source-drainregions, or both. In a portion, in the FD section and the source-drainregions, into which the insulating section extends, the p-n junctiondoes not exist. Therefore, compared to a case where the insulatingsection is not formed, an area of the p-n junction region formed in thebottom surface of the FD section, the bottom surfaces of thesource-drain regions, or both is reduced in accordance with the portioninto which the insulating section extends.

According to an embodiment of the present technology, there is provideda method of manufacturing an imaging device including:

(A) forming a photodiode, for each of pixels, on a top surface of asemiconductor layer, and forming a floating diffusion section and areading circuit on the top surface of the semiconductor layer, thephotodiode being configured to perform photoelectric conversion and togenerate electric charge in accordance with an amount of received light,the floating diffusion section being configured to accumulate theelectric charge generated in the photodiode, and the reading circuitconfigured to output a pixel signal having a voltage in accordance witha level of the electric charge accumulated in the floating diffusionsection; and

(B) concurrently forming a groove portion and a concave portion on abottom surface of the semiconductor layer, the groove portion beingconfigured to electrically separate the photodiode for each of thepixels, and the concave portion extending into part or whole of a bottomsurface of the floating diffusion section, part or whole of a bottomsurface of a source-drain region of a transistor, or both.

In the method of manufacturing the imaging device according to theabove-described embodiment of the present technology, the concaveportion extends into part or whole of the bottom surface of the FDsection, part or whole of the bottom surfaces of the source-drainregions, or both. In a portion, in the FD section and the source-drainregions, into which the concave portion extends, the p-n junction doesnot exist. Therefore, compared to a case where the concave portion isnot formed, an area of the p-n junction region formed in the bottomsurface of the FD section, the bottom surfaces of the source-drainregions, or both is smaller by an area of the portion into which theconcave portion extends.

According to the imaging device, the electronic apparatus, and themethod of manufacturing the imaging device in the above-describedembodiments of the present technology, the area of the p-n junctionregion formed at the bottom surface of one or both of the FD section andthe source-drain region is reduced. Therefore, the p-n junction capacityat the bottom surface of one or both of the FD section and thesource-drain region is effectively suppressed.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a diagram illustrating an example of a schematic configurationof an imaging device according to a first embodiment of the presenttechnology.

FIG. 2 is a diagram illustrating an example of a circuit configurationin a pixel shown in FIG. 1.

FIG. 3 is a diagram illustrating an example of an in-plane layout of thepixel shown in FIG. 1.

FIG. 4 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line A-A in FIG. 3 and viewed from adirection of its arrows.

FIG. 5 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line B-B in FIG. 3 and viewed from adirection of its arrows.

FIG. 6A is a diagram illustrating an example of a cross-sectionalconfiguration of an insulating section and a periphery thereof shown inFIG. 4.

FIG. 6B is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 4.

FIG. 7A is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 4.

FIG. 7B is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 4.

FIG. 8A is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 4.

FIG. 8B is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 4.

FIG. 9A is a diagram illustrating an example of a cross-sectionalconfiguration of an insulating section and a periphery thereof shown inFIG. 5.

FIG. 9B is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 5.

FIG. 10A is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 5.

FIG. 10B is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 5.

FIG. 11A is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 5.

FIG. 11B is a diagram illustrating an example of the cross-sectionalconfiguration of the insulating section and the periphery thereof shownin FIG. 5.

FIG. 12 is a diagram illustrating an example of a step of manufacturingthe imaging device shown in FIG. 1 with the use of a cross-section of aportion corresponding to a portion taken along the line A-A in FIG. 3.

FIG. 13 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to a portion taken along theline B-B in FIG. 3, of a semiconductor layer shown in FIG. 12.

FIG. 14 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 12 with the use of a cross-section ofthe portion corresponding to the portion taken along the line A-A inFIG. 3.

FIG. 15 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 3, of the semiconductor layer shown in FIG. 14.

FIG. 16 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 14 with the use of a cross-section ofthe portion corresponding to the portion taken along the line A-A inFIG. 3.

FIG. 17 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 3, of the semiconductor layer shown in FIG. 16.

FIG. 18 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 16 with the use of a cross-section ofthe portion corresponding to the portion taken along the line A-A inFIG. 3.

FIG. 19 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 3, of the semiconductor layer shown in FIG. 18.

FIG. 20 is a diagram illustrating an example of an in-plane layout of apixel in an imaging device according to a first modification.

FIG. 21 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line A-A in FIG. 20 and viewed from adirection of its arrows.

FIG. 22 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line B-B in FIG. 20 and viewed from adirection of its arrows.

FIG. 23 is a diagram illustrating an example of a step of manufacturingthe imaging device according to the first modification in an in-planelayout.

FIG. 24 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line A-A in FIG. 23 and viewed from adirection of its arrows.

FIG. 25 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line B-B in FIG. 23 and viewed from adirection of its arrows.

FIG. 26 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 24 with the use of a cross-section ofthe portion corresponding to the portion along the line A-A in FIG. 23.

FIG. 27 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 23, of the semiconductor layer shown in FIG. 26.

FIG. 28 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 26 with the use of a cross-section ofthe portion corresponding to the portion taken along the line A-A inFIG. 23.

FIG. 29 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 23, of the semiconductor layer shown in FIG. 28.

FIG. 30 is a diagram illustrating an example of an in-plane layout of apixel in an imaging device according to a second modification.

FIG. 31 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line A-A in FIG. 30 and viewed from adirection of its arrows.

FIG. 32 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line B-B in FIG. 30 and viewed from adirection of its arrows.

FIG. 33 is a diagram illustrating an example of a step of manufacturingthe imaging device according to the second modification in an in-planelayout.

FIG. 34 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line A-A in FIG. 33 and viewed from adirection of its arrows.

FIG. 35 is a diagram illustrating an example of a cross-sectionalconfiguration taken along a line B-B in FIG. 33 and viewed from adirection of its arrows.

FIG. 36 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 34 with the use of a cross-section ofthe portion corresponding to the portion along the line A-A in FIG. 33.

FIG. 37 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 33, of the semiconductor layer shown in FIG. 36.

FIG. 38 is a diagram illustrating an example of a manufacturing stepfollowing the step shown in FIG. 36 with the use of a cross-section ofthe portion corresponding to the portion taken along the line A-A inFIG. 33.

FIG. 39 is a diagram illustrating an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 33, of the semiconductor layer shown in FIG. 38.

FIG. 40 is a diagram illustrating an example of a cross-sectionalconfiguration of an insulating section and a periphery thereof in animaging device according to a third modification.

FIG. 41 is a diagram illustrating another example of the cross-sectionalconfiguration of the insulating section and the periphery thereof in theimaging device according to the third modification.

FIG. 42 is a diagram illustrating an example of a cross-sectionalconfiguration of an insulating section and a periphery thereof in animaging device according to a fourth modification.

FIG. 43 is a diagram illustrating another example of the cross-sectionalconfiguration of the insulating section and the periphery thereof in theimaging device according to the fourth modification.

FIG. 44 is a diagram illustrating another example of the cross-sectionalconfiguration of the insulating section and the periphery thereof in theimaging device according to the fourth modification.

FIG. 45 is a diagram illustrating another example of the cross-sectionalconfiguration of the insulating section and the periphery thereof in theimaging device according to the fourth modification.

FIG. 46 is a diagram illustrating an example of a schematicconfiguration of an imaging module according to a second embodiment ofthe present technology.

FIG. 47 is a diagram illustrating an example of a schematicconfiguration of an electronic apparatus according to a third embodimentof the present technology.

DETAILED DESCRIPTION

Some embodiments of the present technology will be described below indetail with reference to the drawings. The description will be providedin the following order.

1. First Embodiment Imaging Device

An example provided with an insulating section extending into a bottomsurface of a FD, bottom surfaces of source-drain regions, or both

2. Modifications Imaging Device

2.1 First Modification

An example provided with a groove portion

An example using a mask with an aperture having a varying width

2.2 Second Modification

An example provided with a groove portion

An example using a mask with a lattice-shaped opening

2.3 Third Modification

An example provided with a hollow inside a concave portion

2.4 Fourth Modification

An example provided with a film having a negative fixed voltage

3. Second Embodiment Imaging Module 4. Third Embodiment ElectronicApparatus 1. First Embodiment

[Configuration]

FIG. 1 illustrates an example of a schematic configuration of an imagingdevice 1 according to a first embodiment of the present technology. Theimaging device 1 is a CMOS-type solid-state imaging device. The imagingdevice 1 includes a pixel region 11 in which a plurality of pixels 12are arranged in a matrix, and peripheral circuits. The imaging device 1may include, as the peripheral circuits, for example, a vertical drivecircuit 13, a column processing circuit 14, a horizontal drive circuit15, an output circuit 16, and a drive control circuit 17. The pixelregion 11 and the peripheral circuits may be formed, for example, on asemiconductor layer 10 as shown in FIG. 1.

The vertical drive circuit 13 may sequentially select the pixels 12 on arow unit basis, for example. The column processing circuit 14 mayperform a correlated double sampling (CDS) process on a pixel signaloutputted from each of the pixels 12 in a row selected by the verticaldrive circuit 13, for example. The column processing circuit 14 mayextract a signal level of the pixel signal and hold pixel data based onan amount of received light in each of the pixels 12 by performing theCDS process. The horizontal drive circuit 15 may sequentially output thepixel data held by the column processing circuit 14 to the outputcircuit 16, for example. The output circuit 16 may amplify the inputtedpixel data and output the amplified pixel data to an external signalprocessing circuit, for example. The drive control circuit 17 maycontrol drive of each block (the vertical drive circuit 13, the columnprocessing circuit 14, the horizontal drive circuit 15, and the outputcircuit 16) in the peripheral circuits, for example.

FIG. 2 illustrates an example of a circuit configuration of the pixel12. The pixel 12 may include, for example, a photodiode PD, a transfertransistor Tr1, a floating diffusion section FD, and a reading circuit12A. The photodiode PD performs photoelectric conversion and therebygenerates electric charge in accordance with the amount of receivedlight. The photodiode PD is configured of an inorganic material. It isto be noted that the reading circuit 12A may be shared by a plurality ofpixels 12. The reading circuit 12A may include, for example, a resettransistor Tr2, a selection transistor Tr3, and an amplifier transistorTr4. The floating diffusion section FD accumulates the electric chargegenerated in the photodiode PD. The transfer transistor Tr1, the resettransistor Tr2, the selection transistor Tr3, and the amplifiertransistor Tr4 are each configured of a CMOS transistor.

A cathode of the photodiode PD is connected to a source of the transfertransistor Tr1, and an anode of the photodiode PD is connected to areference potential line (for example, to the ground). A drain of thetransfer transistor Tr1 is connected to the floating diffusion sectionFD, and a gate of the transfer transistor Tr1 is connected to a verticalsignal line VSL. The vertical signal line VSL is connected to an outputterminal of the vertical drive circuit 13. A source of the resettransistor Tr2 is connected to the floating diffusion section FD, and adrain of the reset transistor Tr2 is connected to a power line VDD andto a drain of the amplifier transistor Tr4. A gate of the resettransistor Tr2 is connected to the vertical signal line VSL. A source ofthe selection transistor Tr3 is connected to the column processingcircuit 14, and a drain of the selection transistor Tr3 is connected toa source of the amplifier transistor Tr4. A gate of the selectiontransistor Tr3 is connected to the vertical signal line VSL. The drainof the amplifier transistor Tr4 is connected to the power line VDD, anda gate of the amplifier transistor Tr4 is connected to the floatingdiffusion section FD.

When the reset transistor Tr2 is turned on, the reset transistor Tr2resets a potential of the floating diffusion section FD to a potentialof the power line VDD. The selection transistor Tr3 controls a timing ofoutputting the pixel signal from the reading circuit 12A. The amplifiertransistor Tr4 outputs a pixel signal that has a voltage in accordancewith a level of the electric charge generated in the photodiode PD. Whenthe selection transistor Tr3 is turned on, the amplifier transistor Tr4amplifies the potential of the floating diffusion section FD and outputsa voltage in accordance with the amplified potential to the columnprocessing circuit 14.

FIG. 3 illustrates an example of an in-plane layout of the pixel 12.FIG. 4 illustrates an example of a configuration of a cross-sectiontaken along a line A-A shown in FIG. 3. FIG. 5 illustrates an example ofa configuration of a cross-section taken along a line B-B shown in FIG.3. FIG. 3 illustrates an example of the in-plane layout of the pixels 12in a case where the reading circuit 12A is shared by four pixels 12. Thein-plane layout of the pixel 12 is not limited to that shown in FIG. 3.The in-plane layout of the four pixels 12 that share the reading circuit12A is not limited to that shown in FIG. 3.

The pixel 12 may include, for example, the photodiode PD, a PDseparation layer 10S, the transfer transistor Tr1, the floatingdiffusion section FD, and the reading circuit 12A in the semiconductorlayer 10 and on one surface (a top surface) of the semiconductor layer10. The reset transistor Tr2, the selection transistor Tr3, and theamplifier transistor Tr4 that configure the reading circuit 12A may bearranged, for example, in a line. The reset transistor Tr2, theselection transistor Tr3, and the amplifier transistor Tr4 share oneactive region. A drain region 22D of the reset transistor Tr2 alsoserves as a drain 24D of the amplifier transistor Tr4, and a drain 23Dof the selection transistor Tr3 also serves as a source 24S of theamplifier transistor Tr4.

The photodiode PD may be, for example, an impurity diffusion region thatis formed by injecting an impurity into the semiconductor layer 10. Thephotodiode PD is configured of a semiconductor that has a conductivitytype different from that of the PD separation layer 10S. When theconductivity type of the PD separation layer 10S is a p-type, theconductivity type of the photodiode PD is an n-type. The PD separationlayer 10S may be formed, for example, in a region, in the semiconductorlayer 10, in contact with interfaces with the photodiode PD, thetransfer transistor Tr1, the floating diffusion section FD, and thetransistors included in the reading circuit 12A. The PD separation layer10S may be, for example, an impurity diffusion region formed byinjecting an impurity into the semiconductor layer 10.

Gate electrodes 21G, 22G, 23G, and 24G of the transfer transistor Tr1,the reset transistor Tr2, the selection transistor Tr3, and theamplifier transistor Tr4 may each be configured, for example, of apolysilicon electrode. Source regions 22S, 23S, and 24S of the resettransistor Tr2, the selection transistor Tr3, and the amplifiertransistor Tr4 may each be, for example, an impurity diffusion regionformed by injecting an impurity into the semiconductor layer 10. Drainregions 22D, 23D, and 24D of the reset transistor Tr2, the selectiontransistor Tr3, and the amplifier transistor Tr4 may each be, forexample, an impurity diffusion region formed by injecting an impurityinto the semiconductor layer 10 as well. The source regions 22S, 23S,and 24S and the drain regions 22D, 23D, and 24D are each configured of asemiconductor that has a conductivity type different from that of the PDseparation layer 10S. When the conductivity type of the PD separationlayer 10S is a p-type, the conductivity type of the source regions 22S,23S, and 24S and the drain regions 22D, 23D, and 24D is an n-type.

The floating diffusion section FD may be, for example, an impuritydiffusion region formed by injecting an impurity into the semiconductorlayer 10. The floating diffusion section FD is configured of asemiconductor that has a conductivity type different from that of the PDseparation layer 10S. When the conductivity type of the PD separationlayer 10S is a p-type, the conductivity type of the floating diffusionsection FD is an n-type. The floating diffusion section FD, the sourceregions 22S, 23S, and 24S, and the drain regions 22D, 23D, and 24D mayhave bottom surfaces, for example, at substantially the same depth. Forexample, the floating diffusion section FD, the source regions 22S, 23S,and 24S and the drain regions 22D, 23D, and 24D may be formed in thesame manufacturing process (in other words, may be formed concurrently).

Herein, “bottom surface” is a surface that is in a region closer to aback surface of the semiconductor layer 10, and corresponds to the p-njunction surface that is formed as a result of a difference inconductivity type between the above-described impurity diffusion regionsand the PD separation layer 10S. Due to application of a voltage to theabove-described impurity diffusion regions, a depletion region (adepletion region 10D which will be described later) in which carriersare hardly present is formed in “bottom surface” and the vicinitythereof. Because of the difference in impurity concentration, generally,the depletion region 10D is formed to be relatively larger in a regioncloser to the PD separation layer 10S and is formed to be relativelysmaller in a region closer to the above-described impurity diffusionregion.

The imaging device 1 includes the semiconductor layer 10 in the pixelregion 11. Also, the imaging device 1 includes, on one surface (the topsurface) of the semiconductor layer 10, an interlayer insulating film 21including a wiring layer (not illustrated), a planarization layer 22, aclose attachment layer 23, and a support substrate 24. The interlayerinsulating film 21, the planarization layer 22, the close attachmentlayer 23, and the support substrate 24 may be laminated in order on theone surface (the top surface) of the semiconductor layer 10, forexample. The semiconductor layer 10 may be part of a silicon substrate,or part of an SOI (Silicon On Insulator) substrate, for example. Theinterlayer insulating film 21 may include, for example, silicon oxide,SiOF, or SiOC. A gate insulating film, the gate electrodes 22G, 23G, and24G, a metal layer CM, and the like are provided in the interlayerinsulating film 21. The metal layer CM is in contact with a top surfaceof the floating diffusion section FD. The metal layer CM electricallyconnects the floating diffusion section FD to the source region 22S ofthe reset transistor Tr2 and to the gate electrode 24G of the amplifiertransistor Tr4. The planarization layer 22 planarizes asperities on atop surface of the interlayer insulating film 21. The close attachmentlayer 23 closely attaches the planarization layer 22 and the supportsubstrate 24 to each other. The close attachment layer 23 may beconfigured, for example, of a sticking agent, an adhesive agent, or thelike. The support substrate 24 supports the semiconductor layer 10, andmay be configured, for example, of a silicon substrate.

The imaging device 1 may include, on another surface (the back surface)of the semiconductor layer 10, an insulating film 25, a light blockingfilm 26, a planarization layer 27, a color filter layer 28, and anon-chip lens 29 in the pixel region 11, for example. The on-chip lens 29condenses incident light to the photodiode PD for each of the pixels 12.The color filter 28 may transmit light that has a wavelength range of aspecific color (for example, any of red, green, and blue) for each ofthe pixels 12, for example. The color filter 28 includes an insulatingorganic material, and may include, for example, an organic materialhaving a dielectric constant of 4 or smaller. The light blocking film 26prevents part of light that enters one pixel 12 from entering a pixel 12adjacent thereto. The planarization layer 27 planarizes asperitiesformed on the back surface by the light blocking film 26 in order toallow the color filter 28 and the on-chip lens 29 to be formed on aplanarized surface. The insulating film 25 is for reducing the p-njunction capacity in the semiconductor layer 10, and may include, forexample, silicon oxide, SiOF, or SiOC. It is to be noted that theinsulating film 25 may serve as the color filter 28. For example, theinsulating film 25 may be configured of the materials described above asthe materials of the color filter 28. In this case, the color filter 28is omitted.

Next, main part of the imaging device 1 will be described. As shown inFIG. 4, the imaging device 1 may include, for example, an insulatingsection 20 that extends into part or whole of the bottom surface of thefloating diffusion section FD. Moreover, as shown in FIG. 5, the imagingdevice 1 may include, for example, an insulating section 30 that extendsinto part or whole of the bottom surfaces of the source regions 22S and23S of two transistors (the reset transistor Tr2 and the selectiontransistor Tr3). The reset transistor Tr2 and the selection transistorTr3 each correspond to a transistor that has a gate electricallyconnected to the vertical signal line VSL used for selecting the pixel12.

FIGS. 6A, 6B, 7A, 7B, 8A, and 8B each illustrate a cross-sectionalconfiguration of the insulating section 20 and the periphery thereof.The insulating section 20 includes a concave portion 10A that is formedin the PD separation layer 10S in the semiconductor layer 10. Theconcave portion 10A is formed by etching the semiconductor layer 10 fromits back surface and has a columnar shape as will be described later.Therefore, the insulating section 20 has a columnar shape that extendsin a thickness direction of the semiconductor layer 10. The insulatingsection 20 includes a filling layer that fills whole of inside of theconcave portion 10A. This filling layer is formed by filling the wholeof the inside of the concave portion 10A with an insulating film 25.

As shown in FIG. 6A, the concave portion 10A may extend into part of abottom surface 10E of the floating diffusion section FD, for example. Inthis case, a bottom surface (a top surface of the insulating section 20)of the concave portion 10A is located at a position that is away fromthe bottom surface 10E of the floating diffusion section FD by apredetermined distance. “Predetermined distance” refers to a thicknessof a region, in the floating diffusion section FD, that may be thedepletion region 10D. The concave portion 10A may preferably extend to aposition (a so-called neutral region) at which impurity concentration ofthe floating diffusion section FD is 1×10¹⁸ cm⁻³ or higher. Thus, thebottom surface (the top surface of the insulating section 20) of theconcave portion 10A is allowed to be formed avoiding the depletionregion 10D.

As shown in FIG. 6B, the concave portion 10A may be in contact with themetal layer CM, for example. As shown in FIG. 7A, an end of the bottomsurface of the concave portion 10A may extend to outside of the floatingdiffusion section FD, for example. In this case, the end of the bottomsurface of the concave portion 10A may be preferably formed to avoid thedepletion region 10D. As shown in FIG. 7B, the concave portion 10A mayextend into the whole of the bottom surface 10E of the floatingdiffusion section FD, for example. In this case, the end of the bottomsurface of the concave portion 10A may be preferably formed to avoid thedepletion region 10D. As shown in FIG. 8A, the bottom surface of theconcave portion 10A may be rounded, for example. In this case, aportion, of the bottom surface of the concave portion 10A, that has amaximum curvature may be preferably formed to avoid the depletion region10D. As shown in FIG. 8B, for example, an insulating layer 10F may beprovided on part or all of a side face of the floating diffusion sectionFD. The insulating layer 10F may be configured, for example, of a STIdevice separation region that is formed, for example, by filling atrench formed in the semiconductor layer 10 with an insulating film suchas a silicon oxide film. In this case, the concave portion 10A may be incontact with the insulating layer 10F.

FIGS. 9A, 9B, 10A, 10B, 11A, and 11B each illustrate an example of across-sectional configuration of the insulating section 30 and theperiphery thereof. The insulating section 30 includes a concave portion10B that is formed in the PD separation layer 10S in the semiconductorlayer 10. The concave portion 10B is formed by etching the semiconductorlayer 10 from its back surface and has a columnar shape as will bedescribed later. Therefore, the insulating section 30 has a columnarshape that extends in the thickness direction of the semiconductor layer10. The insulating section 30 includes a filling layer that fills wholeof inside of the concave portion 10B. This filling layer is formed byfilling the whole of the inside of the concave portion 10B with theinsulating film 25.

As shown in FIG. 9A, the concave portion 10B may extend into part of abottom surface 10G of the source region 22S or 23S, for example. In thiscase, a bottom surface (a top surface of the insulating section 30) ofthe concave portion 10B is located at a position that is away from thebottom surface 10G of the source region 22S or 23S by a predetermineddistance. “Predetermined distance” refers to a thickness of a region, inthe source region 22S or 23S, that may be a depletion region 10H. Theconcave portion 10B may preferably extend to a position (a so-calledneutral region) at which impurity concentration of the source region 22Sor 23S is 1×10¹⁸ cm⁻³ or higher. Thus, the bottom surface (the topsurface of the insulating section 30) of the concave portion 10B isformed avoiding the depletion region 10H.

As shown in FIG. 9B, the concave portion 10B may be in contact with theinterlayer insulating film 21, for example. As shown in FIG. 10A, an endof the bottom surface of the concave portion 10B may extend to outsideof the source region 22S or 23S, for example. In this case, the end ofthe bottom surface of the concave portion 10B may be preferably formedto avoid the depletion region 10H. As shown in FIG. 10B, the concaveportion 10B may extend into the whole of the bottom surface 10G of thesource region 22S or 23S, for example. In this case, the end of thebottom surface of the concave portion 10B may be preferably formed toavoid the depletion region 10H. As shown in FIG. 11A, the bottom surfaceof the concave portion 10B may be rounded, for example. In this case, aportion, of the bottom surface of the concave portion 10B, that has amaximum curvature may be preferably formed to avoid the depletion region10H. It is to be noted that, as shown in FIG. 11B, for example, aninsulating layer 10J may be provided on part or all of a side face ofthe source region 22S or 23S. The insulating layer 10J may beconfigured, for example, of a STI device separation region that isformed, for example, by filling a trench formed in the semiconductorlayer 10 with an insulating film such as a silicon oxide film.

[Manufacturing Method]

Next, description will be provided of an example of a method ofmanufacturing the imaging device 1. FIGS. 12 to 19 illustrate a processof manufacturing the imaging device 1 in order. FIGS. 12, 14, 16, and 18each illustrate an example of a step of manufacturing the imaging device1 with the use of a cross-section of a portion corresponding to aportion taken along a line A-A in FIG. 3. FIG. 13 illustrates an exampleof a configuration of a cross-section of a portion, corresponding to theportion taken along the line B-B in FIG. 3, of the semiconductor layer10 shown in FIG. 12. FIG. 15 illustrates an example of a configurationof a cross-section of a portion, corresponding to the portion takenalong the line B-B in FIG. 3, of the semiconductor layer 10 shown inFIG. 14. FIG. 17 illustrates an example of a configuration of across-section of a portion, corresponding to the portion taken along theline B-B in FIG. 3, of the semiconductor layer 10 shown in FIG. 16. FIG.19 illustrates an example of a configuration of a cross-section of aportion, corresponding to the portion taken along the line B-B in FIG.3, of the semiconductor layer 10 shown in FIG. 18.

First, a semiconductor substrate 10W is prepared (see FIGS. 12 and 13).The semiconductor substrate 10W may be, for example, a substrateconfigured of an insulating layer 10K and the semiconductor layer 10formed thereon. A typical example of such a substrate may include a SOIsubstrate in which the semiconductor layer 10 is configured of a siliconlayer. It is to be noted that the semiconductor substrate 10W may be abulk silicon substrate. Next, the photodiode PD, the PD separation layer10S, the transfer transistor Tr1, the floating diffusion section FD, andthe reading circuit 12A are formed in the semiconductor layer 10 and onthe top surface thereof. At this time, for example, the floatingdiffusion section FD, and the source regions 22S, 23S, and 24S and thedrain regions 22D, 23D, and 24D may be formed in the same manufacturingprocess (in other words, may be formed concurrently). At this time,further, the interlayer insulating film 21 and the planarization film 22are formed. Subsequently, the support substrate 24 that supports thesemiconductor layer 10 is closely attached to a top surface of theplanarization film 22 with the close attachment layer 23 in between.Thus, a pixel substrate 80 is formed (FIGS. 12 and 13).

Subsequently, for example, a back surface (the semiconductor substrate10W) of the pixel substrate 80 may be etched, for example, by a dryetching method (or by a wet etching method) to reduce a thickness of thesemiconductor substrate 10W to a predetermined thickness. At this time,when the semiconductor substrate 10W is a substrate configured of theinsulating layer 10K and the semiconductor layer 10 formed thereon, thesemiconductor substrate 10W is etched until at least the insulatinglayer 10K is removed (FIGS. 14 and 15).

Subsequently, for example, one concave portion 10A and two concaveportions 10B may be formed by patterning by a dry etching method (or bya wet etching method) using a photolithography method (FIGS. 16 and 17).At this time, the one concave portion 10A and the two concave portions10B are formed to extend into part or whole of the bottom surface of thefloating diffusion section FD and into part or whole of the bottomsurfaces of the source regions 22S and 23S, respectively.

Subsequently, for example, the insulating film 25 may be formed on anentire surface including the one concave portion 10A and the two concaveportions 10B. At this time, the insulating film 25 is formed to fillwhole of inside of the one concave portion 10A and the two concaveportions 10B (FIGS. 18 and 19). Thus, one insulating section 20 and twoinsulating sections 30 are formed. Subsequently, the light blocking film26, the planarization film 27, the color filter 28, the on-chip lens 29,and the like are formed. Thus, the imaging device 1 is manufactured.

[Operation]

Next, an example of an operation of the imaging device 1 will bedescribed. In the imaging device 1, first, the reset transistor Tr2 andthe transfer transistor Tr1 are turned on. Accordingly, a potential ofthe floating diffusion section FD is reset to a potential of the powerline VDD, and a predetermined voltage is applied to the photodiode PD.Subsequently, the reset transistor Tr2 is turned off and the transfertransistor Tr1 is turned on for a predetermined period. During such aperiod, for example, when external light enters the pixel region 11 viaan optical member such as a lens, part of the incident light issubjected to photoelectric conversion in the photodiode PD, and electriccharge of an amount in accordance with intensity of the incident lightis accumulated in each of the pixels 12. The accumulated electric chargeis collected on the transfer transistor Tr1 side by an electric fieldgenerated by a voltage applied to the pixel 12, and is tentativelyaccumulated in the floating diffusion section FD. Subsequently, when thetransfer transistor Tr1 is turned off and the selection transistor Tr3is turned on at a predetermined timing, the potential of the floatingdiffusion section FD is amplified, and a voltage in accordance with theamplified potential is outputted to the column processing circuit 14.

[Effects]

Next, effects of the imaging device 1 will be described. In the imagingdevice 1, the insulating sections 20 and 30 extend into part or whole ofthe bottom surface 10E of the floating diffusion section FD and intopart or whole of the bottom surfaces 10G of the source regions 22S and23S, respectively. The p-n junction does not exist in portions, in thefloating diffusion section FD and the source regions 22S and 23S, intowhich the insulating sections 20 and 30 extend. Therefore, compared to acase where the insulating section 20 or 30 is not formed, an area of thep-n junction region formed on the bottom surface of the floatingdiffusion section FD and on the bottom surfaces of the source regions22S and 23S are reduced in accordance with the portions into which theinsulating sections 20 and 30 extend. As a result, it is possible toeffectively suppress the p-n junction capacity at the bottom surface ofthe floating diffusion section FD and at the bottom surfaces of thesource regions 22S and 23S.

Defects may concentrate near the ends of the bottom surfaces of theconcave portions 10A and 10B in the semiconductor layer 10. In thiscase, a leakage current may flow as a result of the defects. When theends of the bottom surfaces of the concave portions 10A and 10B areformed to avoid the depletion regions 10D and 10H in the presentembodiment, it is possible to avoid defects in image quality (whitespots) resulting from the leakage current, to suppress increase in anoperation current resulting from a dark current, etc.

Moreover, when the concave portion 10A is in contact with the metallayer CM in the present embodiment, time of completion of etching theconcave portion 10A is estimated by detecting a component of the metallayer CM in gas flow in the process of manufacturing the concave portion10A. Similarly, when the concave portions 10A and 10B are in contactwith the insulating layers 10F and 10J, respectively, in the presentembodiment, time of completion of etching the concave portions 10A and10B is estimated by detecting components of the insulating layers 10Fand 10J in gas flow in the process of manufacturing the concave portion10A. Moreover, also when the concave portion 10B is in contact with theinterlayer insulating film 21 in the present embodiment, time ofcompletion of etching the concave portion 10B is estimated by detectinga component of the interlayer insulating film 21 in gas flow in theprocess of manufacturing the concave portion 10B.

2. Modifications

Next, modifications of the imaging device 1 of the above-describedembodiment will be described.

[2.1 First Modification]

[Configuration]

FIG. 20 illustrates an example of an in-plane layout of the pixel 12 inthe imaging device 1 according to a first modification. FIG. 21illustrates an example of a configuration of a cross-section taken alonga line A-A shown in FIG. 20. FIG. 22 illustrates an example of aconfiguration of a cross-section taken along a line B-B shown in FIG.20. FIG. 20 illustrates an example of the in-plane layout of the pixels12 in a case where the reading circuit 12A is shared by four pixels 12.The in-plane layout of the pixels 12 is not limited to that shown inFIG. 20. The in-plane layout of the four pixels 12 that share thereading circuit 12A is not limited to that shown in FIG. 20.

The imaging device 1 according to the present modification includes,together with the insulating sections 20 and 30, separation grooves 40that each insulate between two adjacent photodiodes PD to separate them.The separation groove 40 includes a groove portion 10L that is formed inthe PD separation layer 10S in the semiconductor layer 10. The grooveportion 10L is formed by etching the semiconductor layer 10 from itsback surface as will be described later. The separation groove 40includes a filling layer that fills whole of inside of the grooveportion 10L. This filling layer is formed by filling the whole of theinside of the groove portion 10L with the insulating film 25.

As shown in FIG. 21, for example, the groove portion 10L may have adepth shallower than the depths of the concave portions 10A and 10B, andmay have a width smaller than the widths of the concave portions 10A and10B. As shown in FIGS. 21 and 22, the groove portion 10L is connected tothe concave portion 10A or 10B. Therefore, in a structure in which thegroove portion 10L is connected to the concave portion 10A, a width ofthe structure is relatively larger in the concave portion 10A and isrelatively smaller in the groove portion 10L. Similarly, in a structurein which the groove portion 10L is connected to the concave portion 10B,a width of the structure is relatively larger in the concave portion 10Band is relatively smaller in the groove portion 10L.

Also, the separation groove 40 is connected with the insulating section20 or 30. Therefore, in a structure in which the separation groove 40 isconnected to the insulating section 20, a width of the structure isrelatively larger in the insulating section 20 and is relatively smallerin the separation groove 40. Similarly, in a structure in which theseparation groove 40 is connected to the insulating section 30, a widthof the structure is relatively larger in the insulating section 30 andis relatively smaller in the separation groove 40.

[Manufacturing Method]

Next, description will be provided of an example of a method ofmanufacturing the imaging device 1 according to the presentmodification. FIGS. 23 to 29 illustrate a process of manufacturing theimaging device 1 according to the present modification in order. FIG. 23illustrates an example of a step of manufacturing the imaging device 1with the use of an in-plane layout. FIGS. 24, 26, and 28 each illustratean example of a cross-section of a portion corresponding to a portiontaken along a line A-A in FIG. 23. FIGS. 25, 27, and 29 each illustratean example of a configuration of a cross-section of a portioncorresponding to the portion taken along the line B-B in FIG. 23.

First, the pixel substrate 80 is prepared (see FIGS. 12 and 13).Subsequently, for example, the back surface (the semiconductor substrate10W) of the pixel substrate 80 may be etched, for example, by a dryetching method (or by a wet etching method) to reduce the thickness ofthe semiconductor substrate 10W to a predetermined thickness (see FIGS.14 and 15).

Subsequently, for example, after a resist layer is applied on the entiresurface, the resist layer is patterned by a dry etching method (or a wetetching method) using a photolithography method to form a mask 100 thatincludes openings 110, 120, and 130 (FIGS. 23, 24, and 25). The opening110 is provided in a region that is located between two adjacentphotodiodes PD and extends through a portion directly above the floatingdiffusion section FD. The opening 110 has a belt-like shape. Further,the opening 110 has a wide width portion 111 having a relatively-widewidth in a portion that corresponds to the portion directly above thefloating diffusion region FD, and has a narrow width portion 112 havinga relatively-narrow width in other portions. The opening 120 is providedin a portion that is located between two adjacent photodiodes PD anddoes not extend through the portion directly above the floatingdiffusion section FD. The opening 120 has a belt-like shape that has awidth same as that of the narrow width portion 112. The opening 130 isprovided directly above the reset transistor Tr2, the selectiontransistor Tr3, or the amplifier transistor Tr4. The opening 130 has abelt-like shape. Further, the opening 130 has a wide width portion 131having a relatively-wide width in a portion that corresponds to aportion directly above the source region 22S or 23S, and has a narrowwidth portion 132 having a relatively-narrow width in other portion.

Subsequently, for example, the semiconductor layer 10 may be selectivelyetched with the mask 100 in between. Thus, the concave portion 10A isformed in a portion corresponding to the wide width portion 111, and theconcave portion 10B is formed in a portion corresponding to the widewidth portion 131 (FIGS. 26 and 27). Moreover, the groove portions 10Lare formed in portions corresponding to the openings 120, the narrowwidth portions 112, and the narrow width portions 132 (FIGS. 26 and 27).At this time, the concave portion 10A and the concave portion 10B are soformed as to extend into part or whole of the bottom surface of thefloating diffusion section FD and the bottom surface of the sourceregion 22S or 23S, respectively. Moreover, the groove portion 10L is soformed as not to be in contact with the floating diffusion section FD,the transfer transistor Tr1, and the reading circuit 12A.

The wide width portions 111 and 131 have opening widths larger thanthose of the narrow width portions 112 and 132. Therefore, even if thesame conditions are set for dry etching (or wet etching), thesemiconductor layer 10 is allowed to be etched deeper in the wide widthportions 111 and 131 than in the narrow width portions 112 and 132.Therefore, the dry etching (or the wet etching) may be ended at a timingwhen the concave portions 10A and 10B have extended into the bottomsurface of the floating diffusion section FD and the bottom surface ofthe source region 22S or 23S, respectively.

Subsequently, for example, the insulating film 25 may be formed on anentire surface that includes the concave portions 10A and 10B and thegroove portions 10L. At this time, the insulating film 25 is so formedas to fill whole of the inside of the concave portions 10A and 10B andthe groove portions 10L (FIGS. 28 and 29). Thus, the insulating sections20 and 30 and the plurality of separation grooves 40 are formed.Subsequently, the light blocking film 26, the planarization film 27, thecolor filter 28, the on-chip lens 29, etc. are formed. Thus, the imagingdevice 1 according to the present modification is manufactured.

[Effects]

Next, effects of the imaging device 1 according to the presentmodification will be described. In the imaging device 1, the concaveportions 10A and 10B and the groove portions 10L are formed concurrentlyby selectively etching the semiconductor layer 10 with the mask 100 thathave openings with different widths in between. Accordingly, it ispossible to form the insulating sections 20 and 30 that reduce the p-njunction capacity without increasing the number of manufacturing stepsin the imaging device 1 that includes the separation grooves 40 fordevice separation.

Moreover, in the imaging device 1 according to the present modification,the positions of the wide width portions 111 and 131 in the mask 100 isallowed to be set relatively freely. Therefore, it is possible toconcurrently form the separation grooves 40 for device separation andthe insulating sections 20 and 30 that reduce the p-n junction capacitywhile securing the degree of freedom in the in-plane layout of thepixels 12.

2.2 Second Modification

[Configuration]

FIG. 30 illustrates an example of an in-plane layout of the pixel 12 inthe imaging device 1 according to a second modification. FIG. 31illustrates an example of a configuration of a cross-section taken alonga line A-A shown in FIG. 30. FIG. 32 illustrates an example of aconfiguration of a cross-section taken along a line B-B shown in FIG.30. FIG. 30 illustrates an example of the in-plane layout of the pixels12 in a case where the reading circuit 12A is shared by four pixels 12.The in-plane layout of the pixels 12 is not limited to that shown inFIG. 30. The in-plane layout of the four pixels 12 that share thereading circuit 12A is not limited to that shown in FIG. 30.

The imaging device 1 according to the present modification includes,together with the insulating sections 20 and 30, separation grooves 50that each insulate between two adjacent photodiodes PD to separate them.The separation groove 50 includes a groove portion 10M that is formed inthe PD separation layer 10S in the semiconductor layer 10. The grooveportion 10M is formed by etching the semiconductor layer 10 from itsback surface as will be described later. The groove portion 10M has alattice-like shape, and part of a plurality of portions corresponding tointersections of the lattice each configure the above-described concaveportion 10A or 10B. The separation groove 50 includes a filling layerthat fills whole of inside of the groove portion 10M. This filling layeris formed by filling the whole of the inside of the groove portion 10Mwith the insulating film 25.

As shown in FIG. 31, for example, the groove portion 10M may have adepth shallower than the depths of the concave portions 10A and 10B, andmay have a width almost the same as the widths of the concave portions10A and 10B. As shown in FIGS. 31 and 32, the groove portion 10M isconnected to the concave portion 10A or 10B at the intersection in thegroove portion 10M. Therefore, in a structure in which the grooveportion 10M is connected to the concave portion 10A or 10B, a width ofthe structure is uniform in any portion. Moreover, the separation groove50 is connected to the insulating section 20 or 30 at an intersection inthe separation groove 50. Therefore, in a structure in which theseparation groove 50 is connected to the insulating section 20 or 30, awidth of the structure is uniform in any portion.

[Manufacturing Method]

Next, description will be provided of an example of a method ofmanufacturing the imaging device 1 according to the presentmodification. FIGS. 33 to 39 illustrate a process of manufacturing theimaging device 1 according to the present modification in order. FIG. 33illustrates an example of a step of manufacturing the imaging device 1with the use of an in-plane layout. FIGS. 34, 36, and 38 each illustratean example of a cross-section of a portion corresponding to a portiontaken along a line A-A in FIG. 33. FIGS. 35, 37, and 39 each illustratean example of a configuration of a cross-section of a portioncorresponding to a portion taken along the line B-B in FIG. 33.

First, the pixel substrate 80 is prepared (see FIGS. 12 and 13).Subsequently, for example, the back surface (the semiconductor substrate10W) of the pixel substrate 80 may be etched, for example, by a dryetching method (or by a wet etching method) to reduce the thickness ofthe semiconductor substrate 10W to a predetermined thickness (see FIGS.14 and 15).

Subsequently, for example, after a resist layer is applied on the entiresurface, the resist layer is patterned by a dry etching method (or by awet etching method) using a photolithography method to form a mask 200that includes an opening 210 (FIGS. 33, 34, and 35). The opening 210 isprovided in a region that is located between two adjacent photodiodes PDand has a lattice-like shape. The opening 210 is provided in a regionthat extends through portions directly above the floating diffusionsection FD, the reset transistor Tr2, the selection transistor Tr3, andthe amplifier transistor Tr4. The opening 210 has a width that isuniform in any portion. One intersection region 220 of a plurality ofintersection regions in the opening 210 is provided in a portioncorresponding to the portion directly above the floating diffusionsection FD. Two intersection regions 230 of the plurality ofintersection regions in the opening 210 are provided in portionscorresponding to the portions directly above the source regions 22S and23S, one by one.

Subsequently, for example, the semiconductor layer 10 may be selectivelyetched with the mask 200 in between. Thus, the concave portion 10A isformed in a portion corresponding to the intersection region 220, andthe concave portions 10B are formed in portions corresponding to the twointersection regions 230 (FIGS. 36 and 37). Moreover, the grooveportions 10M are formed in portions (for example, in a linear region 240shown in FIG. 33), of the opening 210, other than the intersectionregions 220 and 230 (FIGS. 36 and 37). At this time, the concave portion10A and the concave portions 10B are so formed as to extend into part orwhole of the bottom surface of the floating diffusion section FD andpart or whole of the bottom surfaces of the source region 22S and 23S,respectively. Moreover, the groove portion 10M is so formed as not to bein contact with the floating diffusion section FD, the transfertransistor Tr1, and the reading circuit 12A.

The intersection regions 220 and 230 have opening widths substantiallylarger than those of the portions, of the opening 210, other than theintersection regions. Therefore, even if the same conditions are set fordry etching (or wet etching), the semiconductor layer 10 is allowed tobe etched deeper in the intersection regions 220 and 230 than inportions, of the opening 210, other than the intersection regions.Therefore, the dry etching (or the wet etching) may be ended at a timingwhen the concave portions 10A and 10B have extended into the bottomsurface of the floating diffusion section FD and the bottom surfaces ofthe source regions 22S and 23S, respectively.

Subsequently, for example, the insulating film 25 may be formed on anentire surface that includes the concave portions 10A and 10B and thegroove portion 10M. At this time, the insulating film 25 is so formed asto fill whole of the inside of the concave portions 10A and 10B and thegroove portions 10M (FIGS. 38 and 39). Thus, the insulating sections 20and 30 and the plurality of separation grooves 50 are formed.Subsequently, the light blocking film 26, the planarization film 27, thecolor filter 28, the on-chip lens 29, etc. are formed. Thus, the imagingdevice 1 according to the present modification is manufactured.

[Effects]

Next, effects of the imaging device 1 according to the presentmodification will be described. In the imaging device 1, the concaveportions 10A and 10B and the groove portions 10M are formed concurrentlyby selectively etching the semiconductor layer 10 with the mask 200 thathas the opening 210 having the lattice-like shape and a uniform width.Accordingly, it is possible to form the insulating sections 20 and 30that reduce the p-n junction capacity without increasing the number ofmanufacturing steps in the imaging device 1 that includes the separationgrooves 50 for device separation.

[2.3 Third Modification]

In the above-described embodiment and the modifications (the firstmodification and the second modification) thereof, the insides of theconcave portions 10A and 10B are filled with the insulating film 25.However, as shown in FIGS. 40 and 41, for example, hollows 20A and 30Amay be provided inside the concave portions 10A and 10B, respectively.

[2.4 Fourth Modification]

In the above-described embodiment and the modifications (the first,second, and third modifications) thereof, part or whole of the insidesof the concave portions 10A and 10B are filled with the insulating film25. However, as shown in FIGS. 42, 43, 44, and 45, for example, theinsulating sections 20 and 30 may each include an insulating film 31that has a negative fixed potential along the inner surfaces of theconcave sections 10A and 10B. The insulating film 31 may include, forexample, HfO₂ or Al₂O₃. The insulating film 31 has a function ofreducing increase of the depletion regions 10D and 10H only near theinterfaces with the concave portions 10A and 10B. Therefore, occurrenceof a leakage current in the intersurfaces with the concave portions 10Aand 10B is suppressed. As a result, it is possible to avoid defects inimage quality (white spots) resulting from the leakage current, tosuppress increase in an operation current resulting from a dark current,etc.

2. Second Embodiment

FIG. 46 illustrates a schematic configuration of an imaging module 2according to a second embodiment of the present technology. The imagingmodule 2 includes the imaging device 1 according to any of theabove-described embodiment and the modifications thereof, and anarithmetic section 41 (a signal processing circuit) that performs apredetermined process on a pixel signal outputted from the imagingdevice 1. The imaging device 1 and the arithmetic section 41 may bemounted, for example, on one wiring substrate. The arithmetic section 41may be configured, for example, of a DSP (Digital Signal Processor).

In the present embodiment, the imaging device 1 according to any of theabove-described embodiment and the modifications thereof is provided.Therefore, it is possible to provide the imaging module 2 that has highimage quality.

3. Third Embodiment

FIG. 47 illustrates a schematic configuration of an electronic apparatus3 according to a third embodiment of the present technology. Theelectronic apparatus 3 includes the imaging module 2 according to theabove-described second embodiment, a lens 42, a display unit 43, and astorage unit 44. The lens 42 allows external light to enter the imagingdevice 1 in the imaging module 2. The display unit 43 displays an imagebased on an output from the imaging module 2. The storage unit 44 storesthe output from the imaging module 2. It is to be noted that theelectronic apparatus 3 may not include the storage unit 44. In thiscase, the electronic apparatus 3 may include a writing unit that writesinformation in an external storage unit.

In the present embodiment, the imaging module 2 according to theabove-described second embodiment is provided. Therefore, it is possibleto provide the electronic apparatus 3 that has high image quality.

Hereinabove, description has been provided referring to some embodimentsand modifications thereof. However, the present technology is notlimited to the above-described embodiments and the like, and may bevariously modified. For example, the imaging device 1 is of aback-surface illumination type in the above-described embodiment and thelike. However, the present technology is also applicable to an imagingdevice of an front-surface illumination type.

It is possible to achieve at least the following configurations from theabove-described example embodiments and the modifications of thedisclosure.

(1) An imaging device including:

a photodiode configured to perform photoelectric conversion and togenerate electric charge in accordance with an amount of received light;

a floating diffusion section configured to accumulate the electriccharge generated in the photodiode;

a reading circuit configured to output a pixel signal having a voltagein accordance with a level of the electric charge accumulated in thefloating diffusion section, the reading circuit including one or aplurality of transistors each having a gate that is electricallyconnected to a wiring used for selecting a pixel; and

an insulating section extending into part or whole of a bottom surfaceof the floating diffusion section, part or whole of bottom surfaces ofsource-drain regions in the one or the plurality of transistors, orboth,

the photodiode, the floating diffusion section, the reading circuit, andthe insulating section being provided in a semiconductor layer.

(2) The imaging device according to (1), wherein the insulating sectionincludes a concave portion formed by etching the semiconductor layerfrom a back surface side thereof, and has a columnar shape.

(3) The imaging device according to (1) or (2), wherein the concaveportion extends into a portion that has impurity concentration of 1×10¹⁸cm⁻³ or higher in the floating diffusion section, the source-drainregions, or both.

(4) The imaging device according to any one of (1) to (3), wherein theinsulating section includes a filling layer configured to fill part orwhole of inside of the concave portion.

(5) The imaging device according to (4), wherein the filling layerincludes one of silicon oxide, SiOF, SiOC, and insulating organicmaterials.

(6) The imaging device according to any one of (1) to (3), wherein theinsulating section has a hollow inside the concave portion.

(7) The imaging device according to any one of (1) to (6), wherein theinsulating section has an insulating film along an inner surface of theconcave portion, the insulating film having a negative fixed electricpotential.

(8) An imaging device according to (7), wherein the insulating filmincludes one of HfO₂ and Al₂O₃.

(9) An electronic apparatus including:

an imaging device; and

a signal processing circuit configured to perform a predeterminedprocess on a pixel signal outputted from the imaging device,

the imaging device including

a photodiode configured to perform photoelectric conversion and togenerate electric charge in accordance with an amount of received light,

a floating diffusion section configured to accumulate the electriccharge generated in the photodiode,

a reading circuit configured to output a pixel signal having a voltagein accordance with a level of the electric charge accumulated in thefloating diffusion section, the reading circuit including one or aplurality of transistors each having a gate that is electricallyconnected to a wiring used for selecting a pixel, and

an insulating section extending into part or whole of a bottom surfaceof the floating diffusion section, part or whole of bottom surfaces ofsource-drain regions in the one or the plurality of transistors, orboth,

the photodiode, the floating diffusion section, the reading circuit, andthe insulating section being provided in a semiconductor layer.

(10) A method of manufacturing an imaging device, the method including:

forming a photodiode, for each of pixels, on a top surface of asemiconductor layer, and forming a floating diffusion section and areading circuit on the top surface of the semiconductor layer, thephotodiode being configured to perform photoelectric conversion and togenerate electric charge in accordance with an amount of received light,the floating diffusion section being configured to accumulate theelectric charge generated in the photodiode, and the reading circuitconfigured to output a pixel signal having a voltage in accordance witha level of the electric charge accumulated in the floating diffusionsection; and

concurrently forming a groove portion and a concave portion on a bottomsurface of the semiconductor layer, the groove portion being configuredto electrically separate the photodiode for each of the pixels, and theconcave portion extending into part or whole of a bottom surface of thefloating diffusion section, part or whole of a bottom surface of asource-drain region of a transistor, or both.

(11) The method according to (10), further including, after forming, onthe bottom surface of the semiconductor layer, a mask having a belt-likeopening that has a wide width portion in part thereof, etching thesemiconductor layer through the mask, and thereby forming the concaveportion in a portion corresponding to the wide width portion in theopening and forming the groove portion in a portion corresponding to aportion other than the wide width portion in the opening.(12) The method according to (10), further including, after forming, onthe bottom surface of the semiconductor layer, a mask having alattice-like opening, etching the semiconductor layer through the mask,and thereby forming the concave portion in a portion corresponding to anintersection of a lattice in the opening and forming the groove portionin a portion corresponding to a portion other than the intersection ofthe lattice in the opening.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A method of manufacturing an imaging device, themethod comprising: forming a photodiode, for each of a number of pixels,on a top surface of a semiconductor layer, and forming a floatingdiffusion section and a reading circuit on the top surface of thesemiconductor layer, the photodiode being configured to performphotoelectric conversion and to generate electric charge in accordancewith an amount of received light, the floating diffusion section beingconfigured to accumulate the electric charge generated in thephotodiode, and the reading circuit configured to output a pixel signalhaving a voltage in accordance with a level of the electric chargeaccumulated in the floating diffusion section; and concurrently forminga groove portion and a concave portion on a bottom surface of thesemiconductor layer, the groove portion being configured to electricallyseparate the photodiode for each of the pixels, and the concave portionextending into a part or a whole of a bottom surface of the floatingdiffusion section, a part or a whole of a bottom surface of asource-drain region of a transistor, or both.
 2. The method according toclaim 1, further comprising, after forming, on the bottom surface of thesemiconductor layer, a mask having a belt-like opening that has a widewidth portion in a part thereof, etching the semiconductor layer throughthe mask, and thereby forming the concave portion in a portioncorresponding to the wide width portion in the opening and forming thegroove portion in a portion corresponding to a portion other than thewide width portion in the opening.
 3. The method according to claim 1,further comprising, after forming, on the bottom surface of thesemiconductor layer, a mask having a lattice-like opening, etching thesemiconductor layer through the mask, and thereby forming the concaveportion in a portion corresponding to an intersection of a lattice inthe opening and forming the groove portion in a portion corresponding toa portion other than the intersection of the lattice in the opening.